To simplify the following discussion, the present invention will be explained in terms of a pointing device for use on a computer; however, the present invention may be utilized with a wide range of data processing systems including hand held computers, cell phones, video games, and the like. Modem computer operating systems and graphics programs require a pointing device for controlling the position of a cursor on the computer display. For desktop PCs, the most successful pointing device is the “mouse”. A mouse is a hand held object that is moved over a flat surface near the keyboard to control the motion of a cursor on the computer display. The direction and distance over which the mouse is moved determines the direction and distance the cursor moves on the display. A conventional mouse provides a rigid object that a user can move with great precision. For a desktop computer, the mouse provides a satisfactory solution to the pointing problem. On the occasion when the workspace is not large enough to provide a path over which the mouse can move and accommodate the desired cursor movement on the display, the user simply picks up the mouse and recenters the mouse in the workspace. Hence, the mouse can provide an almost limitless range of motion.
While the mouse has provided a satisfactory solution to the pointing device problem in the desktop PC market, a similarly successful device is not available for portable and hand-held computers. These computers are often used in environments that lack a sufficiently large flat surface near the keyboard over which a mouse can be moved. Hence, some other form of pointing device is needed when these computers are used in such environments.
A pointing device for use in these environments must solve the problem of moving a cursor quickly and accurately. In addition, the device must operate in an intuitive fashion that a novice user can comprehend without extensive instruction. Further, the pointing device must operate in a limited workspace and fit within the form factor of the computer or hand held device. Finally, the usual constraints of low cost, low power consumption and high reliability must also be met.
In previously filed U.S. patent application Ser. No. 10/722,698, filed Nov. 24, 2003, which is hereby incorporated by reference, a pointing device that meets these requirements is described. The pointing device utilizes a puck that moves in a defined field of motion when a user applies pressure to the puck via the user's finger. When the user releases the puck, a set of springs returns the puck to its centered position within the field of motion. The position of the puck and the pressure on the puck are determined by electrodes in the device. The position information is used to position a cursor on the display screen. Software on the attached device translates the motion of the puck during the time the user's finger is pressing on the puck into the appropriate cursor motion on the device's display. When the user releases the puck, the coupling between the puck and the cursor position is broken by the software, and hence, the cursor does not move backwards while the puck is being recentered.
While the device taught in the above-described patent application provides significant advantages over the dominant prior art solutions to the pointing device problem in the laptop marketplace, there are a number of areas in which improvements would be useful. In particular, it would also be advantageous to provide embodiments in which the ratio of the field of motion to the overall dimensions of the pointing device is as close to unity as possible.